Get poll to return task failure if job/log has been removed.

[wxtim]

Closes #6425

Note

Note to reviewers, you will need to deploy this branch onto remote platforms to confirm it works for remote filesystems.

Finally have a replicable example (Thank you @oliver-sanders)

[scheduling]
    cycling mode = integer
    [[graph]]
        R1 = task

[runtime]
    [[task]]
        script = """
            rm ${CYLC_WORKFLOW_RUN_DIR}/.service/contact
            rm -r "${CYLC_WORKFLOW_RUN_DIR}/log/job/${CYLC_TASK_CYCLE_POINT}/${CYLC_TASK_NAME}"
        """
        platform = _remote_pbs

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included (or explain why tests are not needed).
• Changelog entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[wxtim]

Only test__job_poll_status_files_deleted_logdir is directly related to the PR. Other tests should increase coverage. 😄

[oliver-sanders]

LGTM.

[oliver-sanders]

Note to reviewers, you will need to deploy this branch onto remote platforms to confirm it works for remote filesystems.